1. Field of the Invention
The present invention relates to a novel organic compound and an organic light-emitting device using the same.
2. Related Background Art
An organic light-emitting device is a device in which a thin film comprising a fluorescent organic compound or a phosphorescent organic compound is sandwiched between an anode and a cathode and electrons and holes are injected from the respective electrodes to generate excitons of the fluorescent compound or the phosphorescent compound, whereby light emitted when the excitons return to a ground state is utilized.
According to a study at Kodak company in 1987 (Appl. Phys. Lett. 51, 913 (1987)), there has been reported a light emission of approximately 1000 cd/m2 at an applied voltage of approximately 10 V in a device having a function-separation type two-layer structure using ITO as an anode, a magnesium-silver alloy as a cathode, an aluminum quinolinol complex as an electron-transporting material and a light-emitting material, and a triphenylamine derivative as a hole-transporting material. Related patents include U.S. Pat. Nos. 4,539,507, 4,720,432, and 4,885,211.
In addition, emission of a light within the range of from ultraviolet to infrared light can be generated by changing the type of fluorescent organic compound. In recent years extensive studies have been made on various kinds of compounds. For instance, such compounds are disclosed in U.S. Pat. Nos. 5,151,629, 5,409,783 and 5,382,477, and Japanese Patent Application Laid-Open Nos. H2-247278, H3-255190, H5-202356, H9-202878 and H9-227576.
In recent years, many studies have been made into the application of energy in a triplet state to EL by using a phosphorescent compound as a light-emitting material. A high emission efficiency exhibited by an organic light-emitting device using an iridium complex as a light-emitting material has been reported by a group at Princeton University (Nature 395, 151 (1998)).
Furthermore, in addition to the organic light-emitting device using a low molecular weight material as mentioned above, an organic light-emitting device using a conjugated polymer has been reported by a group at Cambridge University (Nature, 347, 539 (1990)). In this report, light emission from a single layer was confirmed using a film of polyphenylenevinylene (PPV) formed by application. Related patents to an organic light-emitting device using a conjugated polymer include U.S. Pat. Nos. 5,247,190, 5,514,878, 5,672,678, and Japanese Patent Application Laid-Open Nos. H4-145192 and H5-247460.
The recent progress in organic light-emitting devices is remarkable as described above and the characteristics of such devices enable a light-emitting device with a high luminance even at a low applied voltage, a wide range of emission wavelengths, a high-speed response, a small thickness and a light weight, thus suggesting the possibility of application to a variety of uses.
However, the present situation calls for optical output with even higher luminance or higher conversion efficiency. In addition, many problems still remain to be solved regarding durability against the change over time due to long-term use, deterioration caused by atmospheric gas containing oxygen, moisture, or the like. Furthermore, when considering application to a full color display or similar device, the present art is still insufficient against problems relating to the needs for light emission of blue, green, and red with a high color purity.